Two stage crush zone latch

ABSTRACT

A latch ( 10 ) having a housing ( 12, 14, 16, 18 ) to which a ratchet ( 38 ) is pivotably mounted by a rivet ( 40 ) for rotation about a first axis between a latched and unlatched configuration. A slot ( 44 ) extents through the latch and has a first arcuate portion ( 100 ) and a first radial portion ( 102 ). A pawl assembly ( 48, 58, 60, 70 ) has a roller ( 48 ) extending through the slot ( 44 ). The pawl assembly is mounted to the housing for movement of the roller relative to the ratchet ( 38 ) between a first arcuate portion and a first radial portion of the slot. The rivet ( 40 ) is deformable to allow the ratchet ( 38 ) to rotate about the roller axis upon the ratchet ( 38 ) being exposed to an unlatching force above a predetermined level. A flange ( 108 ) extends from the housing across the ratchet ( 38 ) to limit the pivotal movement of the ratchet ( 38 ) about the roller axis.

This application claims the benefit of Provisional application Ser. No.60/133,596, filed May 11, 1999.

FIELD OF THE INVENTION

The present invention relates to vehicle door latches. In particular,this invention relates to a vehicle door latch having a two stage crushzone.

BACKGROUND OF INVENTION

Vehicle door latches must meet specified safety standards. In the UnitedStates of America, the latch must meet Federal Motor Vehicle SafetyStandard (FMVSS) 206 which requires that the latch and striker assemblyshall not separate when a high force is applied. For testing, thelatches are loaded to resist loads in the range of 8,900 to 10,700 N,which results in reaction forces for the ratchet and the pawl pins ofbetween 20,000 and 30,000 N. However, in normal use conditions, thelatch experiences loads in the range of 100 to 300 N which correspondsto a seal force. As a result, conventional latches arc over-designed insize and cost.

SUMMARY OF THE INVENTION

The disadvantages of the prior art may be overcome by providing a latchwhich will meet all of the design criteria, but will have a predictableand controlled deformation during high load conditions to modify forcedirections and locations to the strongest portions of the latch andthereby resist separation.

More particularly, a latch is provided which has a housing and a ratchetpivotably mounted to the housing by a rivet for rotation about a firstaxis between a latched and an unlatched configuration. The housing has aslot extending through it with an arcuate portion generally coaxial withthe first axis and a first radial portion extending generally radiallyaway from the first axis. The latch further has a pawl assembly with aroller extending through the slot and mounted to the housing formovement of the roller relative to the ratchet between the first arcuateportion and the first radial portion of the slot. The roller has aroller axis. The rivet is deformable to allow the ratchet to rotateabout the roller axis upon the ratchet being exposed to an unlatchingforce above a predetermined level. A flange extends from the housingacross the ratchet to limit pivotal movement of the ratchet about theroller axis.

The roller may be mounted to the housing by a pair of wheels, one oneither side of the ratchet, and rotatable relative to the housing abouta second axis generally parallel to the first axis.

The latch may include a ratchet spring acting between the ratchet andthe housing for urging the ratchet toward the unlatched configuration.

The latch may also have a pawl spring extending between the housing andat least one of the wheels for urging the roller toward the arcuateportion of the slot.

The latch may include an actuator having a Bowden cable with an outerportion fixedly secured to the housing and an inner connected to thepair of the wheels for rotating the pair of wheels to move the rollerinto the arcuate portion of the slot.

The ratchet may have a second radial portion spaced apart from the firstradial portion and extending generally radially from the first axis thethe roller may engage the second radial portion to retain the ratchet inthe unlatched configuration. The second radial portion may further havea tapered comer along one side thereof to guide the roller into thearcuate portion of the latch in response to a force tending to move theratchet from its unlatched towards its unlatched configuration.

The latch housing may include a front housing, a rear housing generallyparallel to and spaced apart from the front housing, a front mountingplate adjacent the first housing and a rear mounting plate adjacent therear housing. The ratchet may be mounted between the front and rearmounting plates and each wheel of the pair of wheels may be rotatablymounted to a respective of the front and rear housings.

The flange may be defined by at least one of the front and rear mountingplates.

The ratchet spring may be mounted between the front housing and frontmounting plate and the front housing provided with a recess foraccommodating the ratchet spring. The pawl spring may be mounted betweenthe rear housing and the rear mounting plate provided with a recess foraccommodating the pawl spring.

The rivet may extend between and be secured to the front and rearhousings.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate embodiments of the invention,

FIG. 1 is an exploded perspective view of a latch of the presentinvention;

FIG. 2 is a front elevational view of the latch of FIG. 1 in the open orunlatched position, with cover removed;

FIG. 3 is a front elevational view of the latch of FIG. 1 in the closedor latched position, with cover removed; and

FIG. 4 is a front elevational view of the latch of FIG. 1 under highload test conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a latch 10 of the present invention.The latch 10 comprises a housing including front housing 12, rearhousing 14, front mounting plate 16 and rear mounting plate 18. Each ofthe housings 12 and 14, and the plates 16 and 18 has a U-shaped mouth20, 22, 24 and 26, respectively, which when assembled, a align topresent a mouth which receives a striker (not illustrated). Eachmounting plate 16 and 18 has a central bore 32 and 34, respectively,defining a first axis of rotation 36.

Ratchet 38 is positioned between mounting plates 16, 18 and is pivotallymounted on a rivet 40 through central bore 46. The rivet 40 extendsthrough bores 32, 34 of mounting plates 16, 18. Ratchet 38 has aU-shaped mouth 42. Mouth 42 of ratchet 38 cooperates with the mouth ofthe housing as the ratchet 38 rotates to secure a striker in a latchedcondition.

The ratchet 38 also has a slot 44. Referring to FIGS. 2 and 3, the slot44 has an arcuate portion 100, a first radial portion 102, and a secondradial portion 104. Arcuate portion 100 extends circumferentiallyrelative to the central bore 46. First radial portion 102 is spacedcircumferentially relative to the second radial portion 104. The slot 44receives roller 48 of the pawl assembly.

Referring back to FIG. 1, the pawl assembly generally comprises roller48, wheels 58 and 60 and pawl spring 70.

Mounting plates 16 and 18 each has an arcuate slot 50 and 52,respectively, which align with the radial portions 102 and 104 of slot44 when the latch 10 is assembled. Roller 48 extends through arcuateslots 50 and 52 and is slidable therein. In normal use conditions,roller 48 is floating between the ratchet 38 and the arcuate slots 50and 52.

Front housing 12 and rear housing 14 each has a circular recess 54, 56,respectively, which receives wheels 58 and 60. Wheels 58 and 60 aremounted to rotate about a second axis spaced from the first axis ofrotation 36. Each of wheels 58 and 60 has an axially extending pin 62,64 which engage opposite ends of the roller 48. As is now apparent,rotation of the wheels 58 and 60 moves the roller 48 in the slot 44radially inwardly and outwardly between unlatching and latchingpositions. When roller 48 is radially inwardly, ratchet 38 is free torotate. When the roller 48 is radially outwardly in either the radialportions 102 or 104, the ratchet 38 is prevented from rotating at leastin the unlatching sense. When the roller 48 is radially outward inradial portion 102, the latch 10 is in the latched condition. When theroller 48 is radially outward in radial portion 104 or radially inwardin the distal end of arcuate portion. 100, the latch 10 is in theunlatched condition.

Ratchet spring 66 extends between front housing 12 and the ratchet 38 tobias the ratchet 38 in an open or unlatched condition. Preferably, fronthousing 12 has a recess 68 sized to receive ratchet spring 66.

Pawl spring 70 extends between rear housing 14 and wheel 60 to bias thepawl assembly into a latching condition, i.e. urging roller 48 to theradially outward position or latching position. Preferably, rear housing14 has a recess 69 sized to receive spring 70.

Rear housing 14 has a flange 72 which is spaced from the pawl assembly.Flange 72 has a U-shaped opening 74 which receives Bowden wire 76.Bowden wire 76 is fitted with a U-shaped hooking member 78. The hookingmember 78 has a pair of hooks 80 which engage the pins 82, 84. Actuationof the Bowden wire 76 rotates the pawl assembly against the bias of thepawl spring 70 to move roller 48 from the radially outward position orlatching position to the radially inward position or unlatchingposition. Upon relaxation of the Bowden wire 76, the bias of pawl spring70 returns the pawl assembly back to the latching position

Referring to FIGS. 2 and 3, the operation of the latch 10 of the presentinvention will be described. The arcuate length of arcuate portion 100limits the travel of the ratchet 38 between the fully open or unlatchedposition (FIG. 2) and the closed or latched position (FIG. 3). As theratchet 38 rotates, the mouth 42 of the ratchet 38 cooperates withhousing mouth to latch a striker.

In the open position, roller 48 will be in the distal end of arcuateportion 100. Roller 48 will be rotated inwardly against the bias of pawlspring 70. As the ratchet 38 is rotated in a closing sense in responseto engagement with a striker, the ratchet 38 will rotate initially untilthe roller 48 is able to enter radial portion 104. The bias of pawlspring 70 will urge the roller 48 outwardly allowing the roller 48 tomove outwardly along radial portion 104. In this position, the latch 10will be in the secondary closed condition. Radial portion 104 has atapered comer 106 which biases the ratchet 38 to move in a closing orlatching sense yet prevents rotation in the opening or unlatching sense.

Further rotation of the ratchet 38 in the closing or latching sense,will urge the roller to travel relatively along the arcuate portion 100until the roller 48 is able to travel outwardly along radial portion102. Once roller 48 is in the outward or latching position, ratchet 38is releasably secured in the latched position.

In the latched position, the ratchet 38 is supported at both the pin 40and the roller 48. The pin 40 and the roller 48 cooperate to resist anopening force. To release, the Bowden wire 76 is pulled which responsiverotates wheels 58, 60 which in turn moves roller 48 radially inwardly tothe unlatching position. The bias of ratchet spring 66 rotates theratchet 38 in the unlatching sense releasing the striker.

In order to test the latch according the FMVSS Standards, a test forcein the range of 8,900 to 10,700 N is applied to the ratchet 38 at themouth 42. The ratchet 38 will be urged in the unlatching sense. Theroller 48 will engage the plates 16, 18 and resist further movement ofthe ratchet in the unlatching sense. At this point, further forces willplastically deform pin 40 allowing the ratchet 38 to rotate about theaxis of the roller 48. The ratchet 38 will rotate until it contacts thefront flange 108 of plate 18. Once the ratchet 38 contacts the frontflange 108, the forces transmitted through the pin 40 will reducesignificantly without breakage. The majority of the test forces will betransmitted through the front flange 108 and the plates 16, 18, throughroller 48 and thereby resist opening even under the test forces.

As is now apparent to those skilled in the art, the pin 40 is designedto plastically deform at forces above the normal use conditions, about300 N but well below the test loads of 8,900 to 10,700 N. The pin 40 isdesigned to deform well before the roller 48 deforms. However, if thepin were to break, such failure would not affect the latch response tothe higher loads.

Although the invention has been described with reference to certainspecific embodiments, various modifications thereof will be apparent tothose skilled in the art without departing from the scope of theinvention.

I claim:
 1. A latch comprising: a housing; a ratchet pivotably mountedto said housing by a rivet for rotation about a first axis between alatched and unlatched configuration; said ratchet having a slotextending therethrough with an arcuate portion generally concentric withsaid first axis and a first radial portion extending generally radiallyfrom said first axis; a pawl assembly having a roller extending throughsaid slot and mounted to said housing for movement relative to saidratchet between said first arcuate portion and said first radialportion, said roller having a roller axis, said pawl assemblyoperatively coupled between said housing and said ratchet for movingsaid roller from said arcuate portion of said slot with said ratchet insaid unlatched configuration to said first radial portion of said slotwith said ratchet in said latched configuration; and a flange extendingfrom said housing across said ratchet to limit pivotal movement of saidratchet about said roller axis; whereby said rivet is deformable toforce said ratchet to rotate about said roller axis when said roller isseated in said first radial portion and said ratchet is in said latchedconfiguration upon said ratchet being exposed to an unlatching forceabove a predetermined threshold value.
 2. A latch as claimed in claim 1wherein said roller is mounted to said housing by a pair of wheelsrotatable relative to said housing about a second axis generallyparallel to said first axis, said ratchet extending between said pair ofwheels.
 3. A latch as claimed in claim 2 further having a ratchet springacting between said ratchet and said housing for urging said ratchettoward said unlatched configuration.
 4. A latch as claimed in claim 3further having a pawl spring extending between said housing and at leastone of said wheels for urging said roller toward said arcuate portion ofsaid slot.
 5. A latch as claimed in claim 4 further having an actuatorhaving a Bowden cable with an outer portion fixedly secured to saidhousing and an inner portion connected to said pair of wheels forrotating said pair of wheels to move said roller into said arcuateportion of said slot.
 6. A latch as claimed in claim 1 wherein saidratchet has a second radial portion spaced apart from said first radialportion and extending generally radially from said first axis; saidroller engages said second radial portion to retain said ratchet in saidunlatched configuration; said second radial portion has a tapered corneralong one side thereof to guide said roller into said arcuate portion ofsaid latch in response to a force tending to move said ratchet from saidunlatched configuration toward said latched configuration.
 7. A latch asclaimed in claim 6 wherein said housing includes a front housing, a rearhousing generally parallel to and spaced apart from said first housing;a front mounting plate adjacent said front housing; a rear mountingplate adjacent said rear housing; said ratchet is mounted between saidfront and rear mounting plates; and each wheel of said pair of wheels isrotatably mounted to a respective of said front and rear housings.
 8. Alatch as claimed in claim 7 wherein said flange is defined by at leastone of said front and rear mounting plates.
 9. A latch as claimed inclaim 8 wherein: said ratchet spring is mounted between said fronthousing and said front mounting plate; said front housing has a recessfor accommodating said ratchet spring; said pawl spring is mountedbetween said rear housing and said rear mounting plate; said rearhousing has a recess for accommodating said pawl spring.
 10. A latch asclaimed in claim 9 wherein said rivet extends between and is secured tosaid front and rear housings.